The billboards, paid for the Heartland Institute, are designed to promote the organization's International Congress on Climate Change in Chicago later this month. The Heartland Institute describes itself as a nonprofit devoted to promoting free-market solutions for social and economic problems.

Climate scientists are already reacting to the actions, calling them "truly heinous" and the work of individuals who don't get real global-warming science. In addition, they say the billboards will only bring global-warming skeptics and those who support global warming further apart.

The first billboard, which went up along the Eisenhower Expressway in Maywood, Ill., today, according to a Heartland spokesperson, features a mug shot of Kaczynski with the words "I still believe in Global Warming. Do you?" and a Web address for the Heartland Institute. In a press release, the organization justified this juxtaposition by calling the support for human-caused global warming "nutty."

Climate scientists and mass murderers
Heartland further struck out at Peter Gleick, a prominent climate scientist who leaked internal Heartland documents online in February, revealing the Institute's fundraising efforts and plans to spread doubt about climate change. Heartland claims that one of the documents was faked, referring to the occurrence as "fakegate" in their release.

Gleick says the documents were anonymously mailed to him and he sought the other documents to verify the information. The information in the disputed document is backed up in the other documents, the veracity of which Heartland has not disputed. Individuals named in these documents have confirmed that they were working with Heartland on the plans.

Nevertheless, Heartland has sought to portray itself as on the defensive. In its most recent statement, the organization writes that the leaked memo scandal "revealed that the leaders of the global warming movement are willing to break the law and the rules of ethics to shut down scientific debate and implement their left-wing agendas."

"The people who still believe in man-made global warming are mostly on the radical fringe of society," the statement reads. "This is why the most prominent advocates of global warming aren’t scientists. They are murderers, tyrants, and madmen."

The target of their new campaign, Heartland spokesperson Jim Lakely said, is "people who aren't otherwise following the global-warming debate."

"Heartland is not usually in the provocation business, which is a common tactic of the global-warming alarmists," Lakely told LiveScience. "The reaction to this billboard has been interesting."

Scientists respond
Unsurprisingly, some of the scientists who research climate change took umbrage at this portrayal.

"This is only the latest in a long history of truly heinous actions by the Heartland Institute," said Michael Mann, the Pennsylvania State University climate scientist who originally published the famous "hockey stick" graph showing a rise in average global temperatures after the industrial revolution.

"The only thing I can think of here is that they are acting out of true desperation," Mann told LiveScience.

News of — and jokes about — the billboards quickly spread around the social-networking site Twitter.

"#Heartland Institute believes in gravity. SO DID HITLER," wrote Kevin Borgia, the director of the Illinois Wind Energy Coalition.

"Ted Kaczynsk[i] believes the world is round, and the Heartland Institute tries to persuade people that the world is flat," tweeted Ken Caldeira, an environmental scientist at the Carnegie Institution in Stanford, Calif.

Jason Samenow, a meteorologist at the Washington Post, gave his response in a blog post on the newspaper's website.

"Their approach won't help different perspectives find common ground and work towards the most appropriate path forward," Samenow wrote. "But maybe that's what Heartland, in reality, is fighting against ..."